Bileaflet heart valves are described in U.S. Pat. No. 4,159,543 in which a pair of leaflets pivot along eccentric axes to open and close a blood passageway in response to the pumping of the heart. A single disc occluder which pivots between an open and closed position within an annular heart valve body is described in U.S. Pat. No. 3,546,711. The need continues for improved heart valves which are intended for permanent implantation into the human heart.
In its open position, a valve should provide a passageway which is large and which has good flow characteristics so that blood flows freely therethrough with a minimum of drag and eddy currents. A heart valve should be responsive to blood flow to quickly open during the pumping stroke of the heart and snap back quickly when the heart relaxes to prevent regurgitation of blood. The heart valve must, of course, be biocompatible and thromboresistant, and in this regard, it is important that all surfaces be well washed by blood to prevent stagnation which might lead to eventual clotting. The opening and closing of the valve should be sufficiently soft so as not to cause hemolysis (breaking of blood cells). The heart valve must withstand countless openings and closings, and particular care should be exercised so that the load-bearing surfaces such as the pivot points and stops do not wear out during the life of the patient. The above charactristics are desirably achieved with a simple design which not only simplifies manufacture, but reduces the amount of obstacles to efficient flood flow, reduces the nooks and crannies where blood may stagnate and reduces the quality control problems associated with complexity.